Providing a Downlink Control Structure in a First Carrier to Indicate Information in a Second, Different Carrier

ABSTRACT

A mobile station receives a downlink control structure in a first carrier, where the downlink control structure indicates that control information for the mobile station is on a second, different carrier. The mobile station decodes the control information in the second carrier, where the control information specitl.es resource allocation of a wireless link for the mobile station. More specifically, according to some implementations, the control channel in the first carrier specifies the resource allocation for an extended control channel in the second carrier, where the extended control channel specifies the resource allocation for traffic data of a wireless link for the mobile station.

BACKGROUND

Various wireless access technologies have been proposed or implementedto enable mobile stations to perform communications with other mobilestations or with wired terminals coupled to wired networks. Examples ofwireless access technologies include GSM (Global System for Mobilecommunications) and UMTS (Universal Mobile Telecommunications System)technologies, defined by the Third Generation Partnership Project(3GPP); and CDMA 2000 (Code Division Multiple Access 2000) technologies,defined by 3GPP2.

As part of the continuing evolution of wireless access technologies toimprove spectral efficiency, to improve services, to lower costs, and soforth, new standards have been proposed. One such new standard is theLong Term Evolution (LTE) standard from 3GPP, which seeks to enhance theUMTS technology. The LTE standard is also referred to as the EUTRA(Evolved Universal Terrestrial Radio Access) standard.

More recent developments of LTE have proposed the use of multiplecomponent carriers to increase the available bandwidth of wirelesscommunications. Each component carrier can have a frequency bandwidth ofup to 20 megahertz (MHz). Multiple component carriers are aggregatedtogether to increase the overall bandwidth available to user equipment.Each component carrier appears as an LTE carrier to a mobile station.

An issue associated with using multiple component carriers is that amobile station may have to perform blind decoding of PDCCH (physicaldownlink control channel) in multiple component carriers to findrelevant control information for the mobile station. Such blind decodingmay cause wasteful power consumption at the mobile station.

SUMMARY

In general, according to an embodiment, a method for wirelesscommunication comprises receiving, by a mobile station, a downlinkcontrol structure in a first carrier, where the downlink controlstructure indicates that control information for the mobile station ison a second, different carrier. The mobile station decodes the controlinformation on the second carrier, where the control informationspecifies resource allocation of a wireless link for the mobile station.

Other or alternative features will become apparent from the followingdescription, from the drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are described with respect to thefollowing figures:

FIG. 1 is a block diagram of an example communications network thatincorporates an embodiment of the invention;

FIG. 2 illustrates an example frame structure that incorporates a legacyphysical downlink control channel (PDCCH) and an extended PDCCH(E-PDCCH), according to an embodiment;

FIG. 3 illustrates an example in which a PDCCH in one carrier points tomultiple E-PDCCHs in multiple carriers, in accordance with anembodiment;

FIG. 4 illustrates a PDCCH in one carrier that points to a singleE-PDCCH in another carrier, according to another embodiment;

FIG. 5 illustrates an arrangement in which a carrier pointer message inone carrier points to control information in multiple carriers,according to a further embodiment; and

FIG. 6 is a flow diagram of the process of obtaining control informationby a mobile station, according to an embodiment.

DETAILED DESCRIPTION

In accordance with some preferred embodiments, a technique or mechanismis provided in which a downlink control structure is provided in a firstcarrier, where the downlink control structure indicates that controlinformation for a mobile station is on a second, different carrier. Thedownlink control structure can identify a location of the controlinformation on the second carrier, and the downlink control structurecan also specify the size of the control information on the secondcarrier.

Multiple different carriers, including the first and second carriers,are aggregated to provide an overall bandwidth for wirelesscommunications that is larger than the bandwidth provided by any of theindividual carriers. The mobile station decodes the control informationon the second carrier, where the control information specifies resourceallocation (and other control-related aspects) of a wireless link forthe mobile station.

In accordance with some embodiments, the wireless communicationstechnology that is used is according to the Long Term Evolution (LTE) orEUTRA (Evolved Universal Terrestrial Radio Access) standard from 3GPP(Third Generation Partnership Project), which is an enhancement of theUMTS (Universal Mobile Telecommunications System) wireless technology.Reference to an LTE (or EUTRA) wireless communications network refers tothe wireless communications network that conforms to the requirements ofthe LTE (or EUTRA) standard developed by 3GPP, as that standardcurrently exists or as the standard evolves over time. Note that LTE (orEUTRA) can refer to the current LTE (or EUTRA) standard, or tomodifications of the LTE (or EUTRA) standard that are made over time. Itis expected that in the future a standard that has evolved from LTE (orEUTRA) may be referred to by another name. It is contemplated that theterm “LTE” or “EUTRA” as used herein is intended to cover such futurestandards as well. In alternative embodiments, wireless communicationstechnologies according to other standards can be employed.

In the LTE context, the downlink control structure in a first carrierthat points to control information in at least a second carrier is in aportion of a legacy PDCCH (physical downlink control channel) region.The legacy PDCCH region could be the first few OFDM (orthogonalfrequency division multiplex) symbols of an LTE Release 8 subframe thatare used for transmission of PDCCHs. In some embodiments, the portion ofthe legacy PDCCH region containing the downlink control structure has apredefined compact DCI (downlink control information) format. Thecontrol information in the second carrier can be in the form of anextended PDCCH (E-PDCCH). The mobile station decodes the E-PDCCH toobtain resource allocations (and other control information) for themobile station.

The downlink control structure in the legacy PDCCH region is alsoreferred to as the primary PDCCH, and the primary PDCCH is carried in ananchor carrier that a given mobile station monitors for obtainingcontrol information. Based on detecting the primary PDCCH, the mobilestation can easily identify another carrier that contains the E-PDCCH,which the mobile station can then decode to obtain additional controlinformation, including resource allocation, information indicating amodulation and coding scheme (MCS) (to specify the modulation and codingto apply to traffic data), information relating to a HARQ (hybridautomatic repeat request) process (which specifies the addition of errorcorrection information to a message for error detection and correction),information relating to a redundancy version (RV) (which is an HARQparameter used with incremental redundancy to inform whichretransmission version is used), power control information, and/or othercontrol information. Legacy PDCCH can also be carried by other carriersto support legacy mobile stations.

FIG. 1 shows an example wireless network in which some embodiments ofthe invention can be provided. The wireless network includes a basestation 100 that includes an antenna array or other antenna assembly 102for sending wireless signals into a cell sector 108. A cell sector isone section of a cell of a cellular network. In alternativeimplementations, element 108 can represent an entire cell. Moregenerally, a “cell segment” refers to either a cell or a cell sector.

Although just one base station is depicted in FIG. 1, it is noted that awireless network would typically include multiple base stations. In someembodiments, the wireless network is an LTE wireless network.

In an LTE wireless network, the base station 100 is an enhanced node B(“eNode B”), which includes a base transceiver station that includes theantenna array 102. The base station 100 may also include a radio networkcontroller that cooperates with the enhanced node B. The radio networkcontroller and/or enhanced node B can perform one or more of thefollowing tasks: radio resource management, mobility management formanaging mobility of mobile stations, routing of traffic, and so forth.Note that one radio network controller can access multiple eNode Bs, oralternatively, an eNode B can be accessed by more than one radio accesscontroller.

More generally, the term “base station” can refer to a cellular networkbase station, an access point used in any type of wireless network, orany type of wireless transmitter to communicate with mobile stations.

As depicted in FIG. 1, the base station 100 includes one or more centralprocessing units (CPUs) 122, which is (are) connected to storage 124.Moreover, the base station 100 includes software 126 that is executableon the CPU(s) 122 to perform tasks of the base station 100.

The mobile station 110 of FIG. 1 also includes one or more CPUs 130 thatare connected to storage 132. The mobile station 110 also includessoftware 134 that is executable on the CPU(s) 130 to perform tasks ofthe mobile station 110. In addition, the mobile station 110 includes aninterface 131 to communicate wirelessly with the base station 100.

The base station 100 is connected to a serving and/or packet datanetwork (PDN) gateway 112, which terminates the user plane interfacetoward the enhanced node B and assumes the responsibility for packetrouting and transfer towards an external network 114, which can be apacket data network such as the Internet or other type of network.

The arrangement depicted in FIG. 1 is provided for purposes of example.In other implementations, other wireless network arrangements are used.

As noted above, an advanced version of the LTE standard has proposedperforming carrier aggregation to provide a larger bandwidth. Typically,an LTE component carrier (or more simply “carrier”) supports bandwidthup to 20 megahertz (MHz). However, by aggregating multiple carrierstogether, a larger overall bandwidth can be provided for wirelesscommunications with mobile stations by a base station. The aggregatedcarriers can be contiguous carriers, or alternatively, the aggregatedcarriers do not have to be contiguous.

Note that LTE-advanced mobile stations are able to employ aggregatedcarriers for performing wireless communications with base stations.Legacy LTE mobile stations are only able to employ one carrier.

FIG. 2 shows a frame structure 200 on a particular LTE carrier. Thehorizontal axis of the frame structure 200 represents the time dimension(time slots), while the vertical axis of the frame structure 200represents the frequency dimension (subcarriers of differentfrequencies). The frame structure 200 includes a first region 202 thatcontains various control information, including the legacy (primary)PDCCH. In addition to legacy PDCCHs, the region 202 could include one ormultiple primary PDCCHs. Each primary PDCCH provides the controlinformation for one mobile station or a group of mobile stations. Inaddition, in the example of FIG. 2, the region 202 also includes aphysical control format indicator channel (PCFICH) and a physical hybridautomatic repeat request indicator channel (PHICH). In otherimplementations, the region 202 can include other types of controlchannels.

In accordance with some embodiments, the frame structure 200 alsoincludes another region 204 that includes the E-PDCCH that containsadditional control information. The region 204 may include one ormultiple E-PDCCHs. Each E-PDCCH is to provide additional controlinformation for one mobile station or a group of mobile stations. Aprimary PDCCH on another carrier can identify the location and size ofthe E-PDCCH in the region 204 of the frame structure 200. Similarly, theprimary PDCCH in the region 202 of the frame structure 200 can identifythe location and size of an E-PDCCH on another carrier.

Since the primary PDCCH informs the mobile station the location and sizeof the E-PDCCH on another carrier, the mobile station is able to decodethe E-PDCCH without blind decoding. The primary PDCCH could also be usedto indicate the E-PDCCH on the same carrier.

FIGS. 3 and 4 depict two alternative embodiments of implementing theprimary PDCCH and E-PDCCH. In the FIG. 3 embodiment, a particularprimary PDCCH (e.g., primary PDCCH 302 in a frame structure 200B) on afirst carrier can refer to multiple E-PDCCHs 306A, 306B, 306C, inrespective E-PDCCH regions 304A, 304B, and 304C of respective framestructures 200A, 200B, 200C that are carried in corresponding carriers.Specifically, the primary PDCCH 302 can identify the location and sizeof the E-PDCCH 306A, identify the location and size of the secondE-PDCCH 306B, and identify the location and size of the E-PDCCH 306C.Each of the E-PDCCHs 306A, 306B, and 306C is identified by a carriernumber, location information, and size information.

In one example, the primary PDCCH can have the following format:

-   -   {Carrier #1, E-PDCCH location and size in E-PDCCH region;    -   Carrier #2, E-PDCCH location and size in E-PDCCH region;    -   Carrier #M, E-PDCCH location and size in E-PDCCH region};        where M is the number of carriers supported by the system, or        the number of carriers supported/configured by the base station.        With this option, a separate E-PDCCH is provided per component        carrier, such that each E-PDCCH indicates the resource        assignment on the corresponding individual carrier.

FIG. 4 shows another option, in which the primary PDCCH 302 on onecarrier (carrying frame structure 200B) points to only one E-PDCCH 306Cin another (or the same) carrier. The format of the primary PDCCH inthis example is as follows:

-   -   {Carrier ID, E-PDCCH location and size in E-PDCCH region}

In this example, the primary PDDCH points the mobile station to theE-PDCCH in just one carrier. The E-PDCCH on this carrier indicates theresource assignment across all carriers (i.e., one joint E-PDCCH for allcarriers).

To save the mobile power consumption, the mobile station typicallymonitors an anchor carrier. When the mobile station detects the primaryPDCCH on the anchor carrier, the mobile station turns on itstransceivers on non-anchor carriers and further detects the E-PDCCHs onmultiple carriers. To accommodate the transition time for the mobilestation to turn on the transceivers, the E-PDCCHs could be in a subframewhich is a few subframes later than the subframe containing the primaryPDCCH.

To allow for the mobile station to know the resource allocation(location and size) of an E-PDCCH region, one of several options can beused. In a first option, the location of the starting resource block(RB) and the number of RBs of the E-PDCCH region is indicated. In thecase where distributed virtual RB (DVRB) is used, in which case the RBsthat are allocated are not contiguous, then a gap value can also bespecified.

In a second option, the number of RBs of the E-PDCCH region can bespecified; however, the starting RB is not explicitly specified. Themobile station finds the starting RB location of the E-PDCCH regionusing a predefined frequency hopping pattern that can be a function of acell identifier and a subframe index. An LTE subframe is a portion of anLTE frame, where an LTE frame has a predefined overall time length thatis divided into a predefined number of time slots. An LTE frame is madeup of multiple subframes, where an LTE subframe can include somepredefined number of the time slots (e.g., two slots) of the LTE frame.The subframe index identifies the particular subframe within the overallframe.

For the base station 100 (FIG. 1) to signal to the mobile station theresource allocation of the E-PDCCH region, several options can be used.In a first option, a predefined DCI format is defined to indicate theresource allocation of the E-PDCCH region on each component carrier.This predefined DCI format is provided in the legacy PDCCH region. Also,the CRC (cyclic redundancy check) of the predefined DCI format can bescrambled using a predefined RNTI (radio network temporary identifier)such that only LTE-advanced mobile stations with LTE-advancedmulti-carrier capability are able to decode the predefined DCI format.In some implementations, this predefined RNTI is referred to asLTE-A-RNTI. In other implementations, other scrambling schemes or codingschemes can be applied to specify the predefined DCI format such thatonly LTE-advanced mobile stations that have multi-carrier capability candecode the predefined DCI format. Note that a legacy LTE mobile stationthat does not support multiple carriers would not be able to decode thispredefined DCI format.

In a different option, the base station 100 can use higher layersignaling, such as RRC (radio resource control) signaling, SIB (systeminformation block) signaling, and so forth, to carry the resourceallocation of the E-PDCCH region on each component carrier.

FIG. 5 illustrates an embodiment different from the FIG. 3 and FIG. 4embodiments, in which a carrier pointer message 502 is provided in alegacy PDCCH region that is on the anchor carrier 504 for the mobilestation 110. The carrier pointer message in the anchor carrier 504indicates to the mobile station 110 the non-anchor carrier (e.g.,carrier 506) that the mobile station needs to monitor the PDCCH.Usually, the mobile station would monitor its anchor carrier only. Whenthere are resource allocations on non-anchor carrier(s), the basestation 100 sends a carrier pointer message (such as the carrier pointermessage 502 on the PDCCH of the anchor carrier 504), which is decoded bythe mobile station such that the mobile station can monitor the PDCCH ofthe non-anchor carrier(s), such as non-anchor carrier 506, in the nextsubfranne. The carrier pointer message can also be used to indicate themobile station to monitor the PDCCHs on both anchor and non-anchorcarriers.

Although FIG. 5 shows a one subframe delay between the carrier pointermessage 502 and decoding of PDCCH on a non-anchor carrier, a differentembodiment may allow the mobile station 110 to decode the PDCCH on thenon-anchor carrier in the same subframe.

Some benefits may be provided by some embodiments of the invention. Thedownlink control structure can be used for both contiguous andnon-contiguous spectrum aggregation. To save power, the mobile stationmonitors the downlink control structure of its anchor carrier only, andturns on other component carriers as necessary.

There is limited blind decoding by a mobile station, and no blinddecoding for E-PDCCH due to explicit signaling of location and size ofE-PDCCH. With E-PDCCH, it is convenient to support new DCI formats forLTE-advanced features of relatively large payload size. Also, the newcompact DCI format of the primary PDCCH used to indicate the E-PDCCH isnot expected to have a large payload size, such that it should notoverload the legacy PDCCH region. The E-PDCCH may achieve betterperformance than legacy PDCCH, since inter-cell interference can bebetter controlled on E-PDCCH as it is easier to avoid E-PDCCH collisionfrom neighboring cells.

The E-PDCCH provides control information over the physical downlinkshared channel (PDSCH), which is a downlink traffic channel from thebase station to the mobile station. The information format of theE-PDCCH can be as follows. The E-PDCCH can include a component carriernumber (to identify the associated carrier), resource allocation fordata, MCS information, HARQ process information, uplink power controlinformation, and other control information.

The reserved resource blocks (RBs) of the E-PDCCH can be divided intoresource element groups (REGs) and control channel elements (CCEs) thatcan be used for signaling to different mobile stations. The compact DCIformat of the primary PDCCH carries information on the REGs and/or CCEsto be used by mobile stations. An index to the starting REG and thelength of the allocated REGs are specified. The index can be a physicalREG index or a logical REG index. In the case of the logical REG index,the mapping of logical to physical REGs can be determined through arandom permutation that can be a function of the cell identifier.

FIG. 6 is a flow diagram of a process of wireless communicationsaccording to an embodiment. The tasks of FIG. 6 can be performed by amobile station. The mobile station receives (at 602) a downlink controlstructure in a primary control channel in the legacy PDCCH region in afirst carrier. The downlink control structure identifies the locationand size of extended control information on at least a second differentcarrier. The mobile station decodes (at 604) the downlink controlstructure to find the extended control information, such as the E-PDCCH.The extended control information on the second carrier is decoded (at606) by the mobile station, such that the mobile station is able toretrieve the control information to be used by the mobile station forperforming wireless communications.

Instructions of software described above (including software 126 and 134of FIG. 1) are loaded for execution on a processor (such as one or moreCPUs 122 and 130 in FIG. 1). The processor includes microprocessors,microcontrollers, processor modules or subsystems (including one or moremicroprocessors or microcontrollers), or other control or computingdevices. As used here, a “processor” can refer to a single component orto plural components (e.g., one CPU or multiple CPUs).

Data and instructions (of the software) are stored in respective storagedevices, which are implemented as one or more computer-readable orcomputer-usable storage media. The storage media include different formsof memory including semiconductor memory devices such as dynamic orstatic random access memories (DRAMs or SRAMs), erasable andprogrammable read-only memories (EPROMs), electrically erasable andprogrammable read-only memories (EEPROMs) and flash memories; magneticdisks such as fixed, floppy and removable disks; other magnetic mediaincluding tape; and optical media such as compact disks (CDs) or digitalvideo disks (DVDs). Note that the instructions of the software discussedabove can be provided on one computer-readable or computer-usablestorage medium, or alternatively, can be provided on multiplecomputer-readable or computer-usable storage media distributed in alarge system having possibly plural nodes. Such computer-readable orcomputer-usable storage medium or media is (are) considered to be partof an article (or article of manufacture). An article or article ofmanufacture can refer to any manufactured single component or multiplecomponents.

In the foregoing description, numerous details are set forth to providean understanding of the present invention. However, it will beunderstood by those skilled in the art that the present invention may bepracticed without these details. While the invention has been disclosedwith respect to a limited number of embodiments, those skilled in theart will appreciate numerous modifications and variations therefrom. Itis intended that the appended claims cover such modifications andvariations as fall within the true spirit and scope of the invention.

1.-20. (canceled)
 21. A mobile station, comprising: wirelesscommunication circuitry, configured to perform wireless communicationwith at least a base station; and processing hardware coupled to thewireless communication circuitry, wherein the processing hardware isconfigured to operate with the wireless communication circuitry to:receive, from a base station, control information on a first componentcarrier among a plurality of component carriers, wherein the pluralityof component carriers comprises the first component carrier and a secondcomponent carrier, wherein the second component carrier is differentthan the first component carrier, wherein the control informationindicates a resource assignment for the mobile station on the secondcomponent carrier, and wherein the second carrier is identified in thecontrol information of the first component carrier by a componentcarrier number; and communicate with the base station using the controlinformation of the first component carrier and the resource assignmenton the second component carrier.
 22. The mobile station of claim 21,wherein the processing hardware is further configured to operate withthe wireless communication circuitry to: receive, from the base station,higher layer signaling indicating information for locating controlinformation on at least the first component carrier among the pluralityof component carriers.
 23. The mobile station of claim 21, wherein eachcomponent carrier among the plurality of component carriers appears as aLong-Term Evolution (LTE) carrier.
 24. The mobile station of claim 21,wherein each component carrier among the plurality of component carriershas a separate physical downlink control channel (PDCCH), physicalcontrol format indicator channel (PCFICH), and physical hybrid automaticrepeat request indicator channel (PHICH).
 25. The mobile station ofclaim 21, wherein to communicate with the base station, the processinghardware is further configured to operate with the wirelesscommunication circuitry to receive data from the base station using boththe first carrier and the second carrier.
 26. The mobile station ofclaim 21, wherein the processing hardware is further configured tooperate with the wireless communication circuitry to communicate withthe base station to establish carrier aggregation of the plurality ofcarriers for the mobile station.
 27. The mobile station of claim 21,wherein the first and second carriers are non-contiguous.
 28. The mobilestation of claim 21, wherein the control information is specified inresource blocks (RBs) of a physical downlink shared channel (PDSCH) ofthe first carrier.
 29. The mobile station of claim 21, wherein theprocessing hardware is further configured to operate with the wirelesscommunication circuitry to receive a downlink control structure from thebase station that indicates that the control information is on the firstcarrier; wherein receiving the control information is based on thedownlink control structure.
 30. A non-transitory, computer accessiblememory medium storing program instructions executable by a processor ofa mobile station to: receive, from a base station, control informationon a first component carrier among a plurality of component carriers,wherein the plurality of component carriers comprises the firstcomponent carrier and a second component carrier, wherein the secondcomponent carrier is different than the first component carrier, whereinthe control information indicates a resource assignment for the mobilestation on the second component carrier, and wherein the second carrieris identified in the control information of the first component carrierby a component carrier number; and communicate with the base stationusing the control information of the first component carrier and theresource assignment on the second component carrier.
 31. Thenon-transitory, computer accessible memory medium of claim 30, whereinthe program instructions are further executable to receive, from thebase station, higher layer signaling indicating information for locatingcontrol information on at least the first component carrier among theplurality of component carriers.
 32. The non-transitory, computeraccessible memory medium of claim 30, wherein each component carrieramong the plurality of component carriers appears as a Long-TermEvolution (LTE) carrier.
 33. The non-transitory, computer accessiblememory medium of claim 30, wherein each component carrier among theplurality of component carriers has a separate physical downlink controlchannel (PDCCH), physical control format indicator channel (PCFICH), andphysical hybrid automatic repeat request indicator channel (PHICH). 34.The non-transitory, computer accessible memory medium of claim 30,wherein to communicate with the base station, the program instructionsare further executable to receive data from the base station using boththe first carrier and the second carrier.
 35. The non-transitory,computer accessible memory medium of claim 30, wherein the programinstructions are further executable to communicate with the base stationto establish carrier aggregation of the plurality of carriers for themobile station.
 36. A method for wireless communication, comprising: amobile station, receiving, from a base station, control information on afirst component carrier among a plurality of component carriers, whereinthe plurality of component carriers comprises the first componentcarrier and a second component carrier, wherein the second componentcarrier is different than the first component carrier, wherein thecontrol information indicates a resource assignment for the mobilestation on the second component carrier, and wherein the second carrieris identified in the control information of the first component carrierby a component carrier number; and performing communication with thebase station using the control information of the first componentcarrier and the resource assignment on the second component carrier. 37.The method of claim 36, further comprising: the mobile station,receiving, from the base station, higher layer signaling indicatinginformation for locating control information on at least the firstcomponent carrier among the plurality of component carriers.
 38. Themethod of claim 36, wherein each component carrier among the pluralityof component carriers appears as a Long-Term Evolution (LTE) carrier.39. The method of claim 36, wherein each component carrier among theplurality of component carriers has a separate physical downlink controlchannel (PDCCH), physical control format indicator channel (PCFICH), andphysical hybrid automatic repeat request indicator channel (PHICH). 40.The method of claim 36, wherein the control information is specified inresource blocks (RBs) of a physical downlink shared channel (PDSCH)region of the first carrier, wherein the RBs are divided into resourceelement groups (REGs) and control channel elements (CCEs) that areconfigured for signaling to a plurality mobile stations.